php 中文截取函数

<?php
/*
* 中文字符截取
* @param   string    $string     被处理的字符串
* @param   int        $start       开始截取的位置
* @param   int        $length     截取的字符长度
* @param   string   $charset    字符编码
* @param   string   $dot          缩略符号
*
* @return string
*/function cutstr($string, $start, $length, $charset = "utf-8", $dot = ‘‘) {

if(function_exists("mb_substr")){
    if(mb_strlen($string,$charset)>$length){
      return mb_substr($string,$start,$length,$charset).$dot;
    }
    return mb_substr($string,$start,$length,$charset);
  }
  $new = ‘‘;
  if($charset===‘gbk‘){
    $string = iconv("gbk","utf-8",$string);
  }
  $str = preg_split(‘//u‘,trim($string));
  for($i = $start,$len = 1;$i<count($str)-1 && $len<=$length;$i++,$len++){
    $new .= $str[$i+1];
  }
  if($charset===‘gbk‘){
    $new = iconv("utf-8","gbk",$new);
  }
  return count($str)-2<$length?$new:$new.$dot;
}
echo cutstr(‘暗色调adsa暗色调‘,0,1,‘utf-8‘,‘....‘);
?>